Process for effecting complex



United States. Patent i PROCESS FOR EFFECTING COMPLEX FORMATION William E. Skelton, Beacon, Walter'V. Overbaugh, Fishkill, and Howard A. Kirsch, Wappingers Falls, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application August 15,1950, Serial No. 179,634

8 Claims. (Cl. 260---96.5)

This invention relates to a process for effecting complex formation between a complexing agent such as urea and complex-forming constituents of an organic mixture. The process of the invention is particularly applicable to the dewaxing of lubricating oil stocks by urea complexmg.

In accordance with the process of this invention, complex formation between the complex-forming constituents of an organic mixture and a complexing agent is effected by contacting the organic mixture under agitation conditions at a temperature below about 140 F. with an oxygenated hydrocarbon slurry of complexing agent. After substantially complete complex formation has been effected by contact of organic mixture with oxygenated hydrocarbon slurry, theentire reaction mix ture is subjected to blowing .with a gaslat a temperature below about 140" until substantially allot the oxygenated hydrocarbon solvent has been removed from the mixture. effects precipitation of additional dissolvedcomplex and suspended fines with the result that the slurry is clarified and the separation of solid complex and excess solid complexing agent from the mixture is expedited. Subjection of the agitated mixture to gas blowing efiects a marked improvement in removal of complex-forming constituents from the organic mixture. This improvement is particularly noticeable when it is necessary to meet Freon haze and pour-specifications in preparation of refrigerator oils and low pour diesel oils.

It has recently been discovered that urea and thiourea form solid complexes with certain typesof organic compounds. The class of compounds which complex with urea comprises normal aliphatic hydrocarbons containing at least six carbon atoms, terminal-substituted normal aliphatic hydrocarbons containing at least six carbon atoms, such as n-decanol-and n-dodecylbenzeneand some methyl-substituted n-aliphatic.hydrocarbons Thiourea forms solid complexes with some branched chain hydrocarbons and some naphthenes; triptane, 2 ,3-dimethylbutane are. examples of branched chain hydrocarbons that complex with thiourea; cyclopentane and cyclohex- ,ane-are examples of naphthenes which complex with thiourea. The t-discovery of the complex-forming ability of urea and, thioureaprovidesavery useful tool in the resolution of organic mixtures such as petroleum fractions. Urea complexing is particularly useful in the isolation, ofspecific compounds and in the removal of undesirable components. from petroleum fractions. 7 Dewaxing of petroleum fractions such as gas oils and lubricating oils to produce low waxcontent products illustrates :thetuse of urea complexing to free a petroleum fraction of 1 undesirable constituents. The main commercial usefulness of ureacomplexing at the present timelies in the dewaxing of gas oils and lubricating oil fractions; low pour diesel fuel is in demand as a fuel and for cold weather operation of diesel engines; refrigerator' oils "characterized *bylowpour'and Freon haze test Removal. of solvent from the mixtureare required in air conditioning and refrigeration equipment.

Various procedures have been proposed for effecting complex formation between complexing agents such as urea and complex-forming constituents of organic mixtures. It has been proposed that complex formation be effected by contacting an organic mixture with a saturated or super-saturated solution of urea in a polar solvent such as aliphatic alcohols, aliphatic ketones, water, etc. Complex formation is also effected by contacting an organic mixture with a slurry of complexing agent in a polar solvent. In addition, complex formation is elfected by contacting an organic mixture with a fixed bed of urea wherein the urea is employed in conjunction with a particulate solid which is advantageously an adsorbent. In these various techniques for eifecting complex formation, the presence of a polar compound such as water, an aliphatic alcohol or an aliphatic ketone expedites complex formation.

The process of this invention is directed to the use of the slurry technique for efiecting complex formation and is specific to the use of oxygenated hydrocarbon slurries and particularly to alcoholic slurries. Low molecular weight ketones such as acetone, methyl ethyl ketone may be employed as the slurry media, but low molecular weight alcohols are the usual slurry media. Blowing of the mixtures resulting from stirred contact of organic mixture with slurry of complexing agent and alcohol medium causes substantial evaporation of the alcohol components of the slurry and a resulting substantial clarification of the mixture. Complex and excess complexing agent are readily separated from the blown reaction mixtureto yield a clear oil mixture which is substantially free of complex-forming constituents. Decantation is generally used after gas blowing to separate oil from complex and complex-forming constituents. Filtration may also be used but is generally not required. When the reaction mixture is not blown prior to separation of complex and complexing agent therefrom by decantation, the resulting mixture is cloudy and still contains considerable complex-forming constituents in the form of complex fines or in solution.

The process of the invention is particularly concerned with utilization of urea complexing for the formation to separation of solid and liquid phases is also applicable to thiourea complexing.

In employing alcoholic slurry of urea to dewax gas oils, and lubricating oil fractions, it was discovered that it was necessary to subject the mixture of hydrocarbon oil and alcoholic urea slurry to agitation in order to effect substantial complex formation. On separation of the complex and excess urea from the mixture by decantation. after a settling period, it was discovered that the removal of waxy components from the hydrocarbon fraction was not as complete as expected and the products did not meet the required low pour and Freon haze specifications. This situation was remedied by the improvement of this invention involving blowing the complex-containing mixture with a gas, which is preferably air, for a period of about /2 to 2 /2 hours at a temperature below approximately F. prior to separation of the complex and excess complexing agent.

Apparently alcohols or ketones, which act as a catalyst for complex formation by providing a mutual solvent Patented Sept. 27, 1955 wherein molecular contact of complexing agent and complex-forming constituents can take place, have a substantial solubility for the complex and in addition cause complex fines to remain suspended in the reaction mixture because of its peptizing action on the complex. Alcohol removal from the reaction mixture by blowing with air or other inert gas effects precipitation of dissolved complex and allows suspended fines to settle so that a solid phase comprising complex and excess complexing agent can be removed simply by decantation or filtration. If the reaction mixture is not air blown prior to separation of the solid phase, the suspended fines and dissolved complex remains in the product oil and water washing of the product oil results in the liberation of complexforming constituents. As a consequence, without air blowing it is very difficult to produce a product oil which meets test specifications.

The improvement of this invention permits simple preparation of low pour diesel oil and refrigerator oils which meet test specifications. Employing the improvement of this invention the solid complex and excess complexing agent can be separated from the treated hydrocarbon fraction by filtration or decantation after a settling period. The filtered oil or decanted oil after water washing and drying is characterized by extremely low wax content as indicated by its low pour point or low Freon haze test, depending on whether a diesel fraction or lubricating oil fraction was subjected to the complexing operation.

Prior to the discovery of the advantages of blowing the complex-containing mixture with air or other inert gases prior to separation of complex, it was necessary to subject a decanted oil to blotter pressing or extremely long, commercially inexpedient settling periods prior to water washing and drying in order to obtain finished oils which even approximated test specification. Even blotter pressing and extended settling periods of 40 to 50 hours produced refrigerator oil products which were inferior from a standpoint of Freon haze test to products produced by air blowing for an hour followed by decantation after about a 16-hour settling period. If decantation is employed to separate the oil from the solid phase, settling periods of to 20 hours are used after air blowing the mixture.

The main advantage of the process of the subject invention is that more complete removal of complexforming constituents is effected in a shorter duration of time than was obtainable by former procedures. The low pour of diesel oils and the low Freon haze test of refrigerator oils produced in accordance with the process of this invention are ample proof that the improvement of this invention effects excellent removal of complexforming constituents from mixtures treated in accordance therewith. A second advantage resides in the elimination of troublesome blotter pressing and extended settling times in order to obtain products which approximate test specifications by a complexing process involving the use of alcoholic urea slurry.

The slurry employed in the process of this invention comprises complexing agent and a low molecular weight oxygenated hydrocarbon. Alcohols in the range of C1 to C4 carbon atoms or mixtures of such alcohols are the slurry media. A particularly preferred slurry medium comprises about 40 per cent methanol and 60 per cent isopropanol. This mixture has been found to possess a particularly favorable solubility for both urea and hydrocarbons so that rapid complex formation results from the intimate molecular contact realized with this solvent. It is also possible to modify the alcohol medium by the use of about 2 to per cent solubilizing medium such as acetone, methyl ethyl ketone, etc. Ketones containing about 1 to 5 carbon atoms may also be employed as slurry media. Other low molecular weight oxygenated hydrocarbons containing solubility for both complexing agent and the oil fractions may be employed; for example, esters such as methyl acetate may be used.

Ordinarily sufiicient slurry is employed to maintain a urea dosage of 5 to 50 pounds of urea per barrel of hydrocarbon oil treated and a solvent dosage of approximately 1 to 5 per cent solvent per volume of oil charged. The use of larger amounts of solvent is not detrimental to the complex formation, but is impractical since longer periods of air blowing are required to effect substantial removal of all of the alcohol solvent. Excellent results have been obtained with a slurry charge containing approximately 3 volume per cent solvent per barrel of oil charged, both from the standpoint of rapid complex formation and rapid removal of solvent from the complexcontaining reaction mixture by air blowing.

The urea dosage will depend to a great extent upon the complex-forming constituents present in the oil to be treated. In the manufacture of refrigerator oils, the charged lubricating oils contain a low wax content so that the urea dosage is in the lower portion of the prescribed range, which is in the range of approximately 5 to 17 pounds of urea per barrel of oil. However, with fractions such as gas oil which contain a larger percentage of complex-forming constituents, it is necessary to employ higher urea dosages in the range of 20 to 50 pounds of urea per barrel of oil treated.

It is necessary to agitate the mixture of charge oil and urea slurry in order to obtain rapid and complete complex formation in practical periods of time. Practically any vessel equipped with stirring means may be employed to effect complex formation between the charge oil and the alcoholic urea slurry. As a matter of fact, bottom-totop pumping of the reaction mixture provides sufficient agitation for rapid and complete complex formation in a short period of time.

It has been found that complex formation by contact of an organic mixture with an alcoholic slurry of urea requires approximately 1 to 10 hours in order to effect substantially complete complex formation. Viscous stocks, such as lubricating oil fractions, require contact times in the range of 5 to 10 hours, whereas less viscous stocks, such as gas oils, only require about 1 to 4 hours for substantially complete complex formation. For example, in dewaxing a lubricating oil fraction having a SUS viscosity of 300 at F., approximately 6 hours of agitated contact were required to effect substantially complete complex formation.

Contact between the organic mixture and alcoholic urea slurry under agitation conditions must be effected at temperatures below about 140 F. Advantageously, however, temperatures between 70 and F. are employed during complex formation. When the object of the invention is to remove low molecular weight complexforming constituents such as hexane, heptane and octane, from a gasoline fraction, temperatures between 0 and 50 F. must be employed. In general, however, room temperature has been found to be effective for removal of C10 and higher complex-forming constituents from organic mixtures.

Apparently complex formation does not possess critical pressure limitations. Accordingly, atmospheric pressure is ordinarily employed for the agitated contact of organic mixture and urea slurry, although there is no objection to the use of sub-atmospheric or super-atmospheric pressures if the use of these pressures is dictated by other considerations.

Air is the preferred gas for blowing the complexcontaining mixture, but other inert gases, such as nitrogen, flue gas, and light hydrocarbon gases such as methane, may be employed. The air or other gas is blown through the complex-containing mixture at a relatively rapid rate so that removal of alcohol is effected in a short period of time. It has been found that 22.4 cubic feet of air per cubic foot of complex-containing oil mixture per hour is an air rate which results in rapid evaporation of alcohol without excessive foaming during the blowing period. In general, gas rates of 15 to 30 cubic feet of gas per cubic product in approximatelyone hour. If the. reaction mixture contains a much larger percentage of alcohol, it is necessary to air blow the mixture for. longer periods of time, for example, in the. rangeofQ-t'o 3 hours Since in most instances the process of this invention contemplates the use of approximately 2 to 4 volume per cent alcohol per volume of oil treated, the usual period for air blowing is one half to two hours.

The temperature duringair blowing-must alsobe maintained below 140 F. in -order top'revent decomposition of the complex. Ordinarily air blowing is effected at the same temperature as complex forni'ation. Accordingly, atmospheric temperatures between 70 and 120 F. are employed forair blowing unless the object of theinvention is to remove lower molecularweight complex-forming constituents from a hydrocarbon mixture such as 'na phtha under which circumstance lower-temperatures 'ar'e'=maintained during air blowing.

In the production of low pour diesel oil and low Freon haze refrigerator oils the recovery of normalaliphatic constituents from the complex is not of immediate con-- cern since the production of products which meet test specifications is of paramount importance. However, in order to provide a continuous process, it is necessary to decompose the complex into urea and normal aliphatic constituents and re-use the urea for contacting of more charge oil. The improvement of this invention is independent of the means used to decompose the complex and provide a continuous process. However, a brief discussion of the means of decomposition will be presented from which it will be obvious to one skilled in the art how the process of the subject application can be adapted to continuous operation.

The separated solid phase consisting of complex and excess urea can be treated with an aromatic hydrocarbon solvent such as benzene or with a low molecular weight aliphatic hydrocarbon such as pentane which does not complex at atmospheric conditions with urea whereby the complex-forming components of the complex are liberated from the complex and are dissolved in the solvent; the urea portion of the complex and the urea portion of the solid phase are left in the solid state by this I treatment. The solution of liberated complex-forming constituents can be readily separated from the solid urea and the complex-forming constituents recovered from the solvent by fractional distillation. Temperatures of 100 to 180 F. are recommended for this treatment. The residual solid urea can be slurried with further quantities of alcohol and used to contact further portions of organic mixture.

Another procedure for decomposing the complex involves treating the mixture of complex and excess urea with a hydrocarbon-immiscible urea solvent such as water or methanol, whereby the complex is decomposed with dissolution of urea in the urea solvent. The liberated complex-forming constituents are readily separated from the urea solution in which they are substantially insoluble. Water and low molecular weight alcohols are examples of solvents that may be employed. Temperatures between about 120 and 200 F. should be employed in this procedure. This method of decomposition necessitates recovery of solid urea from solution in order to prepare the urea slurry reagent.

In both of the above-described procedures for decomposing the complex and recovering the urea for re-use, alcohol removed from the reaction mixture by air blowing may be recovered from the air stream by an adsorption additional advantage over the conventionalalcohol vrecovery process which comprises a.disti1lation in the-presence of urea and which is usually accompanied by urea decomposition.

The accompanying examples illustrate-the improved results obtained by subjecting the'complex-fcontaining reaction mixture obtained by agitated contact of a lubricating oil fraction with alcoholic urea. slurry to airblowing .prior to separation of the solid complex and excess urea.

QExamples I and II illustrate the results obtained without air blowing whereas Example III illustrates theimproved ..resu1ts obtainedwith the process of this invention. 7

Example I A lubricating oil fractionjhaving a. Freon-1 2 haze above F. and a Freon-12 floc above #20. Ffwas contacted in a stirred reaction vessel with 40 6()"rnethanolisopropanol slurry of urea; the-'reaction rnixture comprised 14 pounds of urea per barrel of oil treated and I the alcohol solvent was employed in-arifa'mountflequalto 4 volume percent of the oil charge.' "'Aft'erIIO hours of agitated contact the reaction mixture, was allowed to settle for 16 hours and-wasthen decanted. There was obtained a product oil which was characterized by a Freon haze of 55 F. and a Freon floc of -'-75 F.

Example II A lubricating oilfr'action'was treated 'in'sir'nila'r fashion as in Example I, with the difference that the oil was allowed to settle for hours prior to decantation of the oil phase from the solid phase comprising complex and excess complexing agent. The product oil obtained by this treatment was characterized by a Freon haze of F. and a Freon floc of 80 F.

Example 111 A lubricating oil fraction was contacted with a slurry of complexing agent in the proportions prescribed in Example I. After 10 hours of agitated contact, the reaction mixture was blown with air for an hour at an air rate of 22 cubic feet of air per cubic foot of oil mixture per hour. After 16 hours of settling there was obtained by decantation a product oil having a Freon haze of F. and a Freon floc of 80 F.

It will be observed that the product oil obtained by subjecting the reaction mixture to air blowing for a period of one hour and to separation by decantation after a settling period of 16 hours was a superior refrigerator oil to the product oils which were not air blown and which were separated by decantation after settling periods of 16 hours and 50 hours. It is apparent that the process of this invention effects substantial improvement in the preparation of low wax content products by a complexing technique employing an oxygenated hydrocarbon slurry of urea.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the process for efiecting complex formation by agitated contact of a liquid mass comprising an organic mixture containing constituents which form solid complexes with a complexing agent selected from the group consisting of urea and thiourea, and a slurry of said complexing agent in an oxygenated hydrocarbon medium, the improvement which comprises subjecting the entire resulting agitated reaction mixture comprising complex, organic mixture and oxygenated hydrocarbon slurry to blowing with an inert gas for a period of time to remove substantially all of the oxygenated hydrocarbon therefrom prior to separation of the solid phase comprising complex and excess complexing agent from said reaction mixture.

2. In a process for effecting complex formation by agitated contact of a liquid mass comprising a hydrocarbon mixture which contains constituents which complex with a complexing agent selected from the group consisting of urea and thiourea, and an alcoholic slurry of said complexing agent at a temperature below 140 F,. the improvement which comprises subjecting the entire agitated resulting reaction mixture comprising complex, hydrocarbon mixture and alcoholic slurry to blowing with an inert gas at a temperature below 140 F. for a period of time to remove substantially all of the alcohol therefrom prior to separation of a solid phase comprising complex and excess complexing agent from said reaction mixture. v

3. An improvement according to claim 2 in which the reaction mixture is blown with air.

4. An improvement according to claim 2 in which the reaction mixture is blown with an inert gas at a temperature between 70 and 120 F.

5. An improvement according to claim 2 in which the reaction mixture is blown with an inert gas at a gas rate of 15 to 30 cubic feet of gas per cubic foot of complexcontaining oil mixture per hour.

6. An improvement according to claim 2 in which the reaction mixture is blown with air for /2 to 2 hours at an air rate of 20 to 25 cubic feet of air per cubic foot of complex-containing oil mixture per hour.

7. In the process for effecting urea complex formation by agitated contact of a liquid mass comprising a hydrocarbon mixture containing constituents which complex with urea, and an alcoholic slurry of urea at a temperature below 140 F., the improvement which comprises subjecting the entire agitated resulting reaction mixture comprising complex, hydrocarbon mixture and alcoholic urea slurry to blowing with an inert gas at a temperature between and F. until the alcohol is substantially completely removed therefrom, allowing the blown mixture to settle, and decanting the oil phase from a solid phase comprising complex and excess urea.

8. An improvement according to claim 7 in which the reaction mixture is blown with air.

References Cited in the file of this patent UNITED STATES PATENTS 2,386,274 Short et a1. Oct. 9, 1945 2,386,356 Schulze et al. Oct. 9, 1945 2,386,360 Short Oct. 9, 1945 2,386,366 Storment Oct. 9, 1945 2,499,820 Fetterly Mar. 7, 1950 2,557,257 Melrose June 19, 1951 2,577,202 Lien et al Dec. 4, 1951 2,606,140 Arnold et al Aug. 5, 1952 2,619,501 Roy Nov. 25, 1952 OTHER REFERENCES Australian application 17339/47, November 2, 1949. 

1. IN THE PROCESS FOR EFFECTING COMPLEX FORMATION BY AGITATED CONTACT OF A LIQUID MASS COMPRISING AN ORGANIC MIXTURE CONTAINING CONSTITUENTS WHICH FORM SOLID COMPLEXES WITH A COMPLEXING AGENT SELECTED FROM THE GROUP CONSISTING OF UREA AND THIOUREA, AND A SLURRY OF SAID COMPLEXING AGENT IN AN OXYGENATED HYDROCARBON MEDIUM, THE IMPROVEMENT WHICH COMPRISES SUBJECTING THE ENTIRE RESULTING AGITATED REACTION MIXTURE COMPRISING COMPLEX, ORGANIC MIXTURE AND OXYGENATED HYDROCARBON SLURRY TO BLOWING WITH AN INERT GAS FOR A PERIOD OF TIME TO REMOVE SUBSTANTIALLY ALL OF THE OXYGENATED HYDROCARBON THEREFROM PRIOR TO SEPARATION OF THE SOLID PHASE COMPRISING COMPLEX AND EXCESS COMPLEXING AGENT FROM SAID REACTION MIXTURE. 